Printed Circuit Board Reverse Engineering of Impedance Test Coupon Guidelines
Trace geometry from Circuit Board replication must replicate the design requirements. Structures must include ground shielding around the test trace if they are used in the design in order to comprehend the effects of ground shielding on impedance and etch variation.
Slight variations of PCB Reverse Engineering in impedance coupon design will depend on the probing method used for measurement. The items listed below are general guidelines of PCB Board cloning technical data package that can be adapted for use with different types of probing. The differences and descriptions of these different probing techniques are covered in the measurement techniques section of this document.
Traces with ground shielding must both reference their corresponding plane either VSS or VCC. Traces should be single ended with no pad or via at the end of the line to avoid perturbations from the reflected TDR pulse after Reverse Engineering PCB Plate.
Route the traces straight with no bends. Bends can induce ringing on the TDR pulse reducing measurement accuracy. Line length will be dependent on the type of probing.
♦ Handheld probe with ground spanner: minimum of 3 inches long.
♦ Fixed pitch controlled impedance microprobes: minimum of 1 inch.
Microstrip structures must provide a signal pad and pad for reference plane. Stripline structures must provide a signal pad and a pad for each reference Plane after Printed Wiring Board Replication.
Pads for handheld probes should be a minimum of 0.025 inches in diameter with 100 to 150 mils spacing between signal and ground.
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